Intrajudge and Interjudge Reliability of the Stuttering Severity Instrument-Fourth Edition

Area of Science:

• Speech-Language Pathology
• Clinical Linguistics
• Psychometrics

Background:

• The Stuttering Severity Instrument (SSI) is a widely used tool for assessing stuttering severity.
• Previous versions of the SSI have documented limitations impacting its clinical utility.
• The SSI-Fourth Edition (SSI-4) represents the latest iteration of this assessment tool.

Purpose of the Study:

• To evaluate the intra- and interjudge reliability of the Stuttering Severity Instrument-Fourth Edition (SSI-4).
• To compare reliability findings using manual-described methods versus alternative calculation approaches.

Main Methods:

• Twelve trained judges assessed SSI-4 data from videos of adults who stutter at two separate time points.
• Reliability was analyzed for SSI-4 subscores (Frequency, Duration, Physical Concomitants), total score, and final severity rating.
• Data analysis included calculations consistent with the SSI-4 manual and novel calculations of judge agreement.

Main Results:

• Intra- and interjudge reliability for SSI-4 subscores and total score aligned with the manual's reported values when using the manual's calculation methods.
• Alternative calculations of judge agreement yielded different values for subscores, total score, and severity rating compared to the manual.
• New calculations provided reliability data not previously available in the SSI-4 manual.

Conclusions:

• Clinicians and researchers should be aware of the SSI-4's limitations, particularly when using methods beyond those detailed in the manual.
• Further research into the multitasking demands of the SSI-4 may inform strategies to enhance reliability.
• Investigating the impact of data collection methods on specific variables could improve the SSI-4's psychometric properties.